The present invention generally relates to a liquid material dispensing apparatus and, more specifically, to an applicator or module for dispensing controlled patterns of liquid filaments and a nozzle having a asymmetric liquid discharge orifice for controlling the direction in which the liquid filament is discharged.
Many reasons exist for dispensing liquids, such as hot melt adhesives, in the form of a thin filament or strand with a controlled pattern. Conventional patterns used in the past include patterns involving a swirling effect of the filament by impacting filament with a plurality of jets of air. This is generally known as controlled fiberization or CFT"ugr" in the hot melt adhesive dispensing industry. Controlled fiberization techniques are especially useful for accurately covering a wider region of a substrate with adhesive dispensed as single filaments or as multiple side-by-side filaments from nozzle orifices having small diameters, such as on the order of 0.010 inch to 0.060 inch. The width of the adhesive pattern placed on the substrate can be widened to many times the width of the adhesive filament itself. Moreover, controlled fiberization techniques are used to provide better control of the adhesive placement. This is especially useful at the edges of a substrate and on very narrow substrates, for example, such as on strands of material such as Lycra used in the leg bands of diapers. Other adhesive filament dispensing techniques and apparatus have been used for producing an oscillating pattern of adhesive on a substrate or, in other words, a stitching pattern in which the adhesive moves back-and-forth generally in a zig-zag form on the substrate.
Conventional swirl nozzles typically have a central adhesive dispensing orifice surrounded by a plurality of air orifices. The adhesive dispensing orifice is centrally located on a protrusion which is symmetrical in a full circle or radially about the adhesive dispensing orifice. Another advantageous controlled pattern dispenser, disclosed in U.S. patent application Ser. No. 09/571,703 filed on even date herewith and the disclosure of which is hereby incorporated herein by reference, locates the adhesive dispensing orifice on a wedge-shaped member and includes air orifices located in generally surrounding relation at the base of the wedge-shaped member.
One particular problem with conventional nozzles configured to produce a controlled pattern of adhesive by impacting the adhesive filament with air is that manufacturing imperfections or contaminates within the liquid adhesive discharge orifice may cause the discharging filament to be misdirected as the filament exits the discharge orifice. Since controlled fiberization techniques such as this are often utilized for applications requiring a high degree of accuracy, any unintended deflection of the adhesive filament upon discharge must be minimized. As a general illustration, FIGS. 1A and 1B schematically illustrate prior art swirled adhesive patterns 10a, 10b, 10c on a substrate 12 and a liquid discharge passage 20 of a nozzle 22 with a defect 24 shown in exaggerated form in FIG. 1B. This defect 24 causes the discharging filament 26 of adhesive to be deflected as shown in FIG. 1B. As shown in FIG. 1A, one result can be that adjacent patterns 10a, 10b of swirled adhesive filaments on a substrate, which are intended to be evenly spaced as shown in phantom lines, become unevenly spaced as shown in solid lines. FIG. 1C illustrates another problem of the prior art. In this figure a nozzle 21 is dispensing multiple strands or filaments of adhesive 26a, 26b, 26c. Liquid strands or filaments 26a, 26b are interfering with each other or tangling with each other as they exit nozzle 21 due, for example, to defect 24 shown in FIG. 1B. These occurrences can be undesirable or even intolerable for certain applications and are experienced in air assisted filament dispensing and non-assisted filament dispensing.
For the reasons stated above, as well as other reasons, it would be desirable to provide apparatus and methods which minimize or override the effect of manufacturing defects or other reasons for adhesive filaments to be deflected upon discharge and, therefore, to produce more controllable and predictable liquid adhesive filament patterns.
Generally, the present invention provides a liquid dispensing module including a dispenser or module body having a liquid supply passage. In the preferred embodiment, the liquid is hot melt adhesive, but the invention is applicable to other liquids as well, such as other polymeric thermoplastic liquids. A nozzle body is coupled to the module body and includes a liquid supply port, a liquid discharge portion or end and a liquid discharge passage having an orifice or opening in fluid communication with the liquid supply port. The liquid supply port is in fluid communication with the liquid supply passage of the module body. The liquid discharge passage of the nozzle body extends along an axis and the liquid discharge orifice has an asymmetric shape about the axis to provide a controlled directional movement of the liquid filament dispensed from the liquid discharge orifice.
In general, since the invention provides the above-mentioned controlled directional movement of the liquid filament upon discharge, this controlled movement overcomes potential deflections caused, for example, by manufacturing defects or contaminants within the discharge orifice itself or by other sources of unintended deflective movement of the filament. In the preferred embodiment, the substrate is moving beneath the dispenser or module and the controlled movement produced by the asymmetric shape of the orifice or opening at the discharge end is in the machine direction. As the liquid adhesive filament discharges from the orifice, the filament is purposely deflected in the machine direction. This helps prevent sideward deflection of a swirled adhesive pattern or other liquid filament pattern. In this manner, sideward spacing of adjacent patterns of adhesive is maintained as intended without tangling of adjacent patterns, or better edge control is achieved and, generally, more accurate positioning of the liquid is achieved side-to-side beneath the dispenser in a direction transverse to the substrate movement.
In various embodiments of the invention, the controlled movement of the discharged liquid filament and, more particularly, the asymmetric shape of the orifice, is achieved in different manners. As one feature, the notch intersects the liquid discharge passage and causes deflection of the adhesive in the direction of the notch. As another alternative, the discharge portion of the nozzle body may include a chamfer intersecting with the liquid discharge passage. As another alternative, the discharge portion may include a stepped portion intersecting with the liquid discharge passage.
These and other features, advantages and objectives of the invention will become more readily apparent to those of ordinary skill in the art upon review of the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings.